Battery Terminology
Many terms appear when working in the battery space, which can be unclear. Whether you are working directly with battery technology or a consumer looking for a new battery backup system, it is essential to understand the information you are looking for. Many values depend on the chemistry used in the battery, but a general example is provided where possible. Here is a short list of standard terms that will aid you in becoming a battery expert.
Battery management system (BMS): An electronic system that monitors and controls the operation of rechargeable batteries, ensuring their safe, efficient, and reliable performance. It plays a crucial role in managing various aspects of battery operation, including charging, discharging, balancing, and overall health monitoring.
Calendar aging: The natural degradation or deterioration of a battery over time, even when it is not in use.
Capacity (Ah): The amount of electrical energy a battery can store, typically measured in ampere-hours (Ah) or milliampere-hours (mAh). If a battery energy storage system is 100 Ah, it can supply 100 A for one hour, 50 A for two hours, 1 A for 100 hours, or variations thereof before requiring charging.
Capacity fade: The gradual decrease in a battery's capacity over time due to usage, aging, and environmental conditions.
Cell: The basic unit of a battery that generates electricity through chemical reactions. The typical components of a cell are:
Electrode: The conductive material where chemical reactions occur within a battery cell.
Anode: The electrode where oxidation (loss of electrons) occurs during battery discharge.
Cathode: The electrode where reduction (gain of electrons) occurs during battery discharge.
Electrolyte: A substance that conducts electricity by ion movement and facilitates chemical reactions within a battery.
Separator: a porous membrane or material placed between the anode and cathode to prevent electrical short circuits while allowing the flow of ions between the electrodes.
Terminal: The connection point on a battery used for external electrical connections.
Current (A): The flow of electric charge (electrons) through a conductor, measured in amperes (A).
Cycle aging: The degradation or loss of capacity in a rechargeable battery due to repeated charge and discharge cycles.
Depth of discharge (DoD): The percentage of a battery's capacity used during a discharge cycle, indicating how deeply the battery has been discharged.
Overcharge: Supplying more charge to a battery than it can handle, leading to overheating, gas generation, and potential damage.
Self-discharge: The gradual loss of charge in a battery when not in use, typically due to internal chemical reactions.
State of charge (SoC): The current energy level stored within a battery relative to its maximum capacity, typically expressed as a percentage. It indicates how much of the battery's total capacity is currently available for use.
Thermal runaway: Is a self-propagating process in which the temperature of a system increases rapidly due to an internal feedback loop, leading to further temperature increases and potentially catastrophic consequences.
Voltage (V): The electric potential difference between two points determines the force that drives electric current. Voltage is referred to in a few different ways when related to batteries:
Nominal voltage is the average voltage that the battery is designed to provide during regular operation. For example, the nominal voltage of a lithium-ion battery is 3.6 - 3.7 V.
Lower cutoff voltage: The minimum voltage level at which a battery should be discharged to prevent damage, deterioration, or unsafe conditions. For a lithium-ion battery, this is 2.5 - 3.0 V.
Maximum voltage: A battery cell or pack can reach the highest voltage during charging. For lithium-ion batteries, this is between 4.2 - 4.3 V.